For vegetables, depending upon the type, I typically propose these be eaten raw or steamed. For grains and beans, I typically advise these be cooked thoroughly, as this reduces phytate content and makes their fibers more digestible.
There are a few notable exceptions to the notion that raw fruit will nutritionally outperform cooked fruit. One of these is tomato. (Yes, tomato is considered a fruit, though many people will eat tomatoes with vegetables, which is perfectly fine.)
Super tomato nutrition
This is not to say that eating raw tomatoes isn’t pretty dog-gone healthy. Tomatoes contain hundreds of nutrients. Raw tomatoes are excellent or good sources of vitamin C, biotin, molybdenum, vitamin K, vitamin A, vitamin B6, folate, pantothenic acid, vitamin B3, vitamin B1, vitamin E, copper, potassium, manganese, phosphorus, magnesium, chromium, choline, zinc, iron and protein. One cupful of raw tomatoes will also contain over two grams of fiber.
Tomatoes also contain numerous phytocompounds. These include carotenoids such as lycopene, lutein, zeaxanthin, alpha- and beta-carotene; flavonols such as rutin, kaempferol and quercetin; flavonones such as naringenin and chalconaringenin; caffeic acid; ferulic acid; coumaric acid; esculeoside A; octadecadienoic acid and others.
Now a few of these compounds – those that are heat-sensitive – are depleted when tomatoes are cooked. However, there is significant evidence now pointing to the fact that cooking tomatoes makes many of tomatoes’ healthiest compounds more bioavailable to the body.
Let’s look at some recent evidence:
Tomatoes have more cardiovascular benefits when cooked
A 2016 study from the Medicine School at the University of Barcelona, along with researchers from Spain’s Biomedical Research Centre in Physiopathology of Obesity and Nutrition (CIBEROBN) studied the comparative effects of raw and cooked tomatoes on the cardiovascular system.
The researchers tested 40 healthy people over a period of four months. For one day of each month, after 8 hours of fasting (overnight) they each randomly ate one of four ‘feedings’:
1) Raw tomatoes: 7 grams per kilo (about 2.2 lbs.) of body weight
2) Tomato sauce: 3.5 grams per kilo of body weight
3) Tomato sauce cooked with olive oil: 3.5 grams per kilo of body weight
4) sugar dissolved in water: 0.25 grams per kilo of body weight
The amount of sugar was determined to match the calorie level of the other groups.
The researchers then studied the cardiovascular effects of each upon the subjects. Cardiovascular markers were tested before each feeding and six hours after the consumption of the tomato products or the sugar control.
The cardiovascular testing included total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, and a number of inflammatory markers: This included interleukin-10 (IL-10) and IL-6. They also tested each subjects’ vascular cell adhesion molecule-1 (VCAM-1) – a test that determines artery health and/or stiffness. They also tested markers for immune health such as lymphocyte function-associated antigen-1 (LFA-1) from T-cells and CD36 from monocytes. They also tested each subject’s blood pressure.
The researchers found that practically every cardiovascular marker above was significantly improved after the subjects ate the raw tomatoes, the cooked tomato sauce and the tomato sauce with olive oil.
This includes significantly lower triglycerides, lower blood pressure (both systolic and diastolic), lower LDL-c, and lower total cholesterol. HDL-cholesterol levels increased.
To give you an idea of significance, the subjects’ triglyceride levels went down by 22.6 mg/dL in the raw tomato group.
Nearly all the artery health markers mentioned above were also improved after eating the tomato products, and immunity markers were also improved. For example, raw tomatoes reduced pro-inflammatory IL-6 levels by 0.30 pg/mL.
However, to the surprise of the researchers, nearly every parameter improved by the tomato products was more improved in the tomato sauce group compared to the raw tomato group. With the examples above, the tomato sauce reduced triglycerides by 28.4 mg/dL and reduced IL-6 by 0.55 pg/mL.
Furthermore, those markers were even higher in the group that ate the tomato sauce blended with olive oil. With the example above, IL-6 levels went down by 1.09 pg/mL in the tomato sauce with olive oil group.
Triglycerides were the exception in the tomato sauce/olive oil group. Triglycerides only went down by 15 mg/dL in this group (yet this is still very significant). The other improved markers were all better in the tomato sauce with olive oil group.
Why were the tomato sauces healthier?
When the researchers analyzed the nutrient components of each of these tomato products, they found that the cooked tomato sauce had greater levels of carotenoids than the raw tomatoes, including lutein (0.38 sauce to 0.20 raw micrograms/gram), alpha-carotene (0.73 to 0.15), beta-carotene (323 to 246), Z-lycopene isomers 1 (12.4 to 5.53) and E-lycopene (39.3 to 36.7)
The cooked tomato sauce also had more polyphenols, more flavonoids, more flavanones, more flavanols, more phenolic acids (5.38 to 2.47) and more total polyphenols (159 to 110).
While the potential for concentrating these nutrients exist during processing, the researchers adjusted for that. They concluded the increased availability was complex:
“Nutrient bioavailability from dietary sources depends on several factors including the breakup of the food matrix, cooking processes and the presence or addition of lipids or other substances. Moreover, nutrients may interact between them or with other dietary components during digestion, changing their bioavailability.”
The researchers also mentioned that they investigated the effects of the olive oil in itself and determined that the addition of the olive oil helped make the tomatoes nutrients more bioavailable than either the raw or the tomato sauce by itself. This is despite the fact that many nutrient levels were a bit higher in the tomato sauce compared to the tomato sauce with olive oil.
Still, the tomato sauce with olive oil had significantly greater levels of nutrients than the raw tomatoes.
This increase in polyphenol bioavailability after blending with oil and cooking was also confirmed by some of the same researchers in a related 2016 study.
How about ketchups and tomato juice?
Other studies have investigated ketchups and tomato juice for their nutrient content. A 2012 study from the University of Barcelona found ketchups contain practically all of the same compounds.
Personally, I would warn that many tomato ketchups often also contain added refined sugar, which would defeat some of the anti-inflammatory effects of the tomatoes.
With regard to tomato juice: In a study from Spain’s University of Murcia, researchers tested 18 women who drank half a liter (500 milliliters) per day of tomato juice for 15 days. The researchers found that drinking plain tomato juice reduced the women’s artery inflammatory factors (artery adhesion molecules) VCAM-1 and ICAM-1 by 47%.
Tomatoes reduce hardening of arteries
Other research has confirmed that lycopene, the carotenoid that makes tomatoes red, lowers the risk of hardening of the arteries. A 2011 study from researchers at the San Camillo de Lellis Hospital Cardiology Unit in Foggia, Italy, used ultrasonic testing and blood tests to determine that those with higher blood levels of lycopene have significantly reduced incidence of atherosclerosis in the carotid artery.
The study examined 120 human subjects. After complete physical exams and blood testing, ultrasonic testing determined their level of thickening of the artery walls in the carotid artery. The carotid artery travels from the heart to the brain. A hardening of that artery can lead to reduced blood flow to the brain, along with stroke and heart attack.
The analysis found that 58 of the subjects had progressive carotid atherosclerosis. Those with carotid atherosclerosis had higher concentrations of triglycerides, LDL-cholesterol, and total cholesterol in their bloodstreams. They also had lower levels of lycopene.
The researchers concluded that, “These data suggest that higher serum levels of lycopene may play a protective role versus cardiovascular diseases, in particular carotid atherosclerosis.”
This study confirms mounting evidence for lycopene as a potent antioxidant. Antioxidants reduce the hardening of the arteries because they neutralize lipid oxidizing radicals that harm the cells of artery walls.
Tomatoes and the Mediterranean Diet
The Mediterranean Diet benefits the heart according to a number of studies. This is because this diet has undergone intense scientific scrutiny over the past four decades, with the result that it is one of the healthiest diets.
Certainly, tomato sauce with olive oil is one of the hallmarks of the Mediterranean Diet. In fact, tomatoes or tomato sauce in one form or another are eaten frequently by those who eat the Med diet.
So go ahead, have that pizza or pasta with lots of tomato sauce and olive oil. But don’t forget to eat your vegetables and some raw fruits too.
Organic tomatoes taste better and are more nutritious according to other research.
REFERENCES:
Valderas-Martinez P, Chiva-Blanch G, Casas R, Arranz S, Martínez-Huélamo M, Urpi-Sarda M, Torrado X, Corella D, Lamuela-Raventós RM, Estruch R. Tomato Sauce Enriched with Olive Oil Exerts Greater Effects on Cardiovascular Disease Risk Factors than Raw Tomato and Tomato Sauce: A Randomized Trial. Nutrients. 2016 Mar 16;8(3). pii: E170. doi: 10.3390/nu8030170.
Martínez-Huélamo M., Vallverdú-Queralt A., Lecce G.D., Valderas-Martínez P., Tulipani S., Jáuregui O., Escribano-Ferrer E., Estruch R., Illan M., Lamuela-Raventós R.M. Bioavailability of tomato polyphenols is enhanced by processing and fat addition: Evidence from a randomized feeding trial. Mol. Nutr. Food Res. 2016 doi: 10.1002/mnfr.201500820.
García-Alonso FJ, Jorge-Vidal V, Ros G, Periago MJ. Effect of consumption of tomato juice enriched with n-3 polyunsaturated fatty acids on the lipid profile, antioxidant biomarker status, and cardiovascular disease risk in healthy women. Eur J Nutr. 2012 Jun;51(4):415-24.
Vallverdú-Queralt A, Martínez-Huélamo M, Arranz-Martinez S, Miralles E, Lamuela-Raventós RM. Differences in the carotenoid content of ketchups and gazpachos through HPLC/ESI(Li( ) )-MS/MS correlated with their antioxidant capacity. J Sci Food Agric. 2012 Aug 15;92(10):2043-9. doi: 10.1002/jsfa.5598.
Riccioni G, Scotti L, Di Ilio E, Bucciarelli V, Ballone E, De Girolamo M, D’ Orazio N, Martini F, Aceto A, Bucciarelli T. Lycopene and preclinical carotid atherosclerosis. J Biol Regul Homeost Agents. 2011 Jul-Sep;25(3):435-41.